1. ASTR/GEOL-2040: Search for life in the Universe, Lecture 7
Ad69 6
Carbon in the Universe
Miller/Urey experiment
Murchison meteorite
Pages in RGS
ASTR-2040: Lecture 7, Sep 13, 2017
Axel Brandenburg
(Office hours: Mondays 2:30 – 3:30 in X590
and Wednesdays in D230)

2. Organic matter in the Universe
Carbon comes from nuclear fusion in stars
Late stages of evolution
an “old” sun

3. Stellar evolution …are stars alive? Stars consume food (H)
Expell waste (light, gas, dust)
Grow (protostar, main sequence, giant)
Die, and produce offspring from their dust
…are stars alive?

4. Stellar “evolution” No Darwinian evolution
This ”life” cycle is more like a motor
But let’s now look at their waste...

5. Similarity of spectra with coal
Circumstellar envelope of IRAS
Aromatic carbons common in space
Coal – the very bottom of bottom-up approach
p.15 of RGS

6. Molecules around stars
smallest H2
CO, CO2
HCOOH
CH3-CH2-OH
NH3, HCN
H2S, N2O
C60, C70
largest

7. Darwin’s early ideas (letter to Hooker of 1871)
”... we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc, present that a protein compound was chemically formed ready to undergo still more complex changes”

8. Notes of music Carl Sagan: Ramming right molecules together
Building blocks like notes to the music
Not the music itself
Ramming right molecules together
as unlikely as hearing Beethooven’s 9th when letting monkeys loose with roomfull of instruments

9. Putting the right molecules together
Need to produce order
 drive away from equilibrium
Energy required to generate & sustain order

10. Comparison with Frankenstein experiment
Reducing atmosphere:
H2, H2O, NH3, CH4,
Oparin/Haldane
Discharges
Steam

11. After 1 week…. Brown substance
Glycine, alanine, (valine, proline, ...)

12. Role of minerals Support Selection Catalysis
Amino acids polymerize on surfaces
Selection
Different crystal faces select left/right
Both possible  natural selection chose one
Catalysis
N2 to N3H via metalic surfaces
Suitable in hydrothermal vents

13. Minerals as Templates? How could first RNA “genetic” strands arise?
Lab experiments: clays + water + organics  complex organics, including RNA strands.
Repeating chemical structure of minerals may facilitate assembly of complex organics!
clay (microscopic image)
pyrite

14. Meteorites: organics from space
Stony:
Chondrites: 86%
Ordinary (80% of those)
Carbonateous (5% of those)
....
Achondrites:8%
Iron: 6%
Chelyabinsk
(2013)
1500 people injured!

15. Meteorites: different types
Stony:
Chondrites: 86%
Ordinary (80% of those)
Carbonateous (5% of those)
....
Achondrites:8%
Iron: 6%

16. Murchison meteorite September 28, 1969, 10:58 am, Melbourne
Observed as fireball, w/ smoke for 30s
Broke up into pieces, altogether >100kg
Carbonaceous chondrite
Smelly when found
Analyzed like moon rocks
>15 amino acids, etc

17. Comparison Reducing atmosphere: H2, H2O, NH3, CH4, Discharges Steam x
not used
in life x x x x x x x

18. Organics in Muchison & Life
Long polymers absent (single sugars, no proteins)
No nucleotide nor nucleic acids

19. Monomers of building blocks: …what is not found
amino acids
sugars
nucleotides
lipids
none (all are found)

20. Monomers of building blocks …what is not found
amino acids
sugars
nucleotides
lipids
none (all are found)

21. Organics in Muchison & Lifex x x x
Long polymers absent (single sugars, no proteins)
No nucleotide nor nucleic acids
X: building block of life ( all present in Muchison!)

22. The importance of the Miller/Urey experiment is
It proved beyond doubt that life could have arisen natually on Earth;
it showed that natural chemical reactions can produce building blocks for life;
it showed that clay can catalyze the production of RNA.

23. The importance of the Miller/Urey experiment is
It proved beyond doubt that life could have arisen natually on Earth;
it showed that natural chemical reactions can produce building blocks for life;
it showed that clay can catalyze the production of RNA.

24. Check by elimination
proved beyond doubt that life could have arisen natually on Earth?
There was no life in this experiment
Just amino acids and other organics
showed that clay can catalyze the production of RNA?
Clays were not involved here

25. The importance of the Miller/Urey experiment is
It proved beyond doubt that life could have arisen natually on Earth;
it showed that natural chemical reactions can produce building blocks for life;
it showed that clay can catalyze the production of RNA.

26. What this really tells us:
Making many of the building blocks is easy
delived from space
early atmospheric ?reducing conditions
Deep-sea vents (discussed later)
Heat & pressure from impacts
Many possibilities  no conclusive answ.
Unclear how to assemble them

27. What we talked about Carbon produced in stars!
Planetary system made of star dust
Meteorites deliver amino acids and some of the bases of DNA
Similar to Miller/Urey experiment
Organics easy to make  no proofs they have to come from space

28. Next time Electrolysis experiment Delivery by comets
2H2O  2H2 + O2
Delivery by comets
Panspermia Reading:
RGS pp , 28-29
Lon pp
BS pp